.. note::

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.. _per_button:

2.2 Button
=================

In this project, we will learn how to turn on or off the LED by using a button.

**Required Components**

In this project, we need the following components. 

It's definitely convenient to buy a whole kit, here's the link: 

.. list-table::
    :widths: 20 20 20
    :header-rows: 1

    *   - Name	
        - ITEMS IN THIS KIT
        - LINK
    *   - Kepler Kit	
        - 450+
        - |link_kepler_kit|

You can also buy them separately from the links below.


.. list-table::
    :widths: 5 20 5 20
    :header-rows: 1

    *   - SN
        - COMPONENT	
        - QUANTITY
        - LINK

    *   - 1
        - :ref:`cpn_pico_w`
        - 1
        - |link_picow_buy|
    *   - 2
        - Micro USB Cable
        - 1
        - 
    *   - 3
        - :ref:`cpn_breadboard`
        - 1
        - |link_breadboard_buy|
    *   - 4
        - :ref:`cpn_wire`
        - Several
        - |link_wires_buy|
    *   - 5
        - :ref:`cpn_resistor`
        - 2(220Ω, 10KΩ)
        - |link_resistor_buy|
    *   - 6
        - :ref:`cpn_led`
        - 1
        - |link_led_buy|
    *   - 7
        - :ref:`cpn_button`
        - 1
        - |link_button_buy|

**Wiring**


|button0|


* One side of the button pin is connected to 3.3v, and the other side pin is connected to GP14, so when the button is pressed, GP14 will be high. 
* However, when the button is not pressed, GP14 is in a suspended state and may be high or low. In order to get a stable low level when the button is not pressed, GP14 needs to be reconnected to GND through a 10K pull-down resistor.


**Code**

.. note::

    * You can refer to the image below to write code by dragging and dropping. 
    * Import ``2.2_button.png`` from the path of ``kepler-kit-main\piper``. For detailed tutorials, please refer to :ref:`import_code_piper`.


|2.2_button|

After connecting Pico W, click the **Start** button and the code starts to run. When the button is pressed, the LED will be lit. When the button is released, the LED will go out.


**How it Works?**

When the button is pressed, pin14 is high. So if the read pin14 is high, turn the pin15 on (LED is lit); else, turn off the pin15 (LED is off).

* [if () do () else ()]: This is a judgment block, depending on the condition after the [if] block to determine whether to run the blocks inside the [do] block, or the blocks inside the [else] block.
* [is pin () HIGH]: This is used to read the level of a specific pin, if the level read is the same as the set HIGH/LOW, then execute the blocks inside [do] block, otherwise execute the blocks inside [else].